Model 921 Single Gas Analyzer
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Model 921 Single Gas Analyzer DC LU C/) LU DC DCLU Benefits II No moving parts — Reduced noise levels and maintenance II Accuracy better than 0.25 ppm S02 II Excellent baseline stability, minimal span drift II Linearity better than 1% over 4 orders of magnitude II No interference from H2O and CO2 II Optional O2 measurement II Serial communication with plant DCS II PC-User interface software The Need The Model 921 is a rugged single gas analyzer housed in a single 19-inch, rack-mounted unit which can be integrated into CEM systems or used alone for a variety of gas monitoring applications. The Model 921’s no-moving-parts design was specifically developed to enable the high sensitivity, low concentration measurements required by the latest environmental regulations. The Model 921 can be configured to measure most gas species that absorb in the UV. The optional low range white cell provides longer path length for measuring lower concentrations. For example, the minimum full scale for SO2 is 25 ppm, with an accuracy of 1% of full scale. The simple and robust design of the Model 921 is complemented by powerful data processing capabilities. The user-friendly keyboard enables programming of such variables as timing and frequency of local zero and span checks and calibration gas values. A serial communications interface enables direct interfacing with data acquisition and control systems using Modbus protocol. When your requirement is for a rugged, low concentration, gas analyzer, free of interferences from water and CO2, the Model 921 is your answer. The Measurement The Western Research® Model 921 uses our proprietary high resolution UV technology in a dual beam, dual wavelength configuration. The major innovation in the Model 921 is that it is a true dual beam, dual wavelength analyzer with no moving parts. Instead of using a filter/chopper wheel to alternate between measure and reference wavelengths, the Model 921 uses a fixed optical configuration and pulsed UV lamps. This leads to increased light throughput, reduced noise levels, and reduced maintenance. The dual beam configuration combined with the reference measurement ensures low noise performance with minimal baseline and span drift. Resolution better than 0.02 nm is provided by high intensity, line source lamps. These sources emit at a fixed wavelength, providing great measurement stability, and emit low total power, removing the potential for sample photolysis. The high resolution enables unparalleled linearity over a wide dynamic range (less than 1 % deviation over 4 to 5 orders of magnitude) which, in turn, leads to simple, robust data analysis. Applications II Source testing II Continuous emissions monitoring, new and retrofit — Low range SO2 II Manufactured gas QA — Calibration, medical, and industrial gases II SRU tail gas clean-up — H2S and SO2 II Research

Model 921 Single Gas Analyzer Methodology: Dual wavelength, high resolution, nondispersive UV Species Measured (see Note 1) Minimum Full Scale (see Note 2) Maximum Full Scale Note 1: Other species include: NH3, COS, CS2, mercaptans. Note 2: Minimum full scale is based on +1% full scale accuracy over 24 hours with auto zero disabled. Optional O2: Integral paramagnetic sensor Accuracy: Typically better than 1% full scale Repeatability: Typically ±0.5% of full scale Linearity: Typically better than ±1% of full scale Response Time: Typically less than 30s to T90 (excluding sample system) Number...